Stirling refrigerating machine

ABSTRACT

A Stirling refrigerating machine, comprising a regenerator provided in a flow path for a working medium reciprocating between an expansion space and a compression space formed in a cylinder, wherein a flow strengthener making uniform the flow of the working medium passing through the regenerator is provided on one or both of the expansion and compression space sides of the regenerator, whereby, because the nonuniformity of the flow of the working medium passing through the regenerator is improved, a regenerated heat exchanging efficiency can be increased, and thus the performance of the refrigerating machine can be increased.

TECHNICAL FIELD

[0001] The present invention relates to a Stirling refrigeratingmachine.

BACKGROUND ART

[0002]FIG. 3 is a sectional view schematically showing an example of aconventional Stirling refrigerating machine. First, the structure ofthis conventional Stirling refrigerating machine will be described withreference to FIG. 3. A cylinder 1 has a cylindrical space formed insideit, and, in this space, a displacer 2 and a piston 3 are arranged so asto form a compression space 6 and an expansion space 7, between which aregenerator 8 is provided to form a closed circuit. This closed circuithas its working space filled with working gas such as helium, and thepiston 3 is made to reciprocate along its axis (in the direction markedF) by an external power source such as a linear motor (not shown) or thelike. The reciprocating movement of the piston 3 causes periodicpressure variations in the working gas sealed in the working space, andcauses the displacer 2 to reciprocate along its axis.

[0003] A displacer rod 4 penetrating the piston 3 is, at one end, fixedto the displacer 2 and, at the other end, connected to a spring 5. Thedisplacer 2 reciprocates along its axis inside the cylinder 1 with thesame period as but with a different phase from the piston 3. As thedisplacer 2 and the piston 3 move with an appropriate phase differencekept between them, the working gas sealed in the working space forms athermodynamic cycle well-known as the reversed Stirling cycle, andproduces cold mainly in the expansion space 7.

[0004] The regenerator 8 is a matrix of fine wire or a ring-shaped gapformed by wounding foil. As the working gas moves from the compressionspace 6 to the expansion space 7, the regenerator 8 receives heat fromthe working gas and stores the heat. As the working gas returns from theexpansion space 7 to the compression space 6, the regenerator 8 returnsthe heat stored in it to the working gas. Thus, the regenerator 8 servesto store heat.

[0005] Reference numeral 9 represents a high-temperature-side heatexchanger, through which part of the heat generated when the working gasis compressed in the compression space is rejected to outside. Referencenumeral 10 represents a low-temperature-side heat exchanger, throughwhich heat is taken in from outside when the working gas expands in theexpansion space 7.

[0006] Now, how this structure works will be described briefly below.When compressed by the piston 3, the working gas in the compressionspace 6 moves, as indicated by the solid-line arrow A in the figure,through the regenerator 8 to the expansion space 7. Meanwhile, the heatof the working gas is rejected through the high-temperature-side heatexchanger 9 to outside, and thus the working gas is precooled as theresult of its heat being stored in the regenerator 8. When most of theworking gas has flowed into the expansion space 7, it starts expanding,and produces cold in the expansion space 7.

[0007] Next, the working gas moves, as indicated by the broken-linearrow B in the figure, through the regenerator 8 back to the compressionspace 6. Meanwhile, the working gas takes in heat from outside throughthe low-temperature-side heat exchanger 10, and collects the heat storedin the regenerator 8 half a cycle ago before entering the compressionspace 6. When most of the working gas has returned to the compressionspace 6, it starts being compressed again, and thus proceeds to the nextcycle. This cycle is repeated continuously, and cryogenic cold isthereby produced.

[0008] In this structure, the regenerator 8 is realized, for example,with film of polyester or the like wound in a cylindrical shape.However, here, variations are inevitable in the gaps between differentlayers of the film so wound, and therefore, when such a regenerator isincorporated in a Stirling refrigerating machine, most of the workinggas flows through where the gaps are relatively large, and little of itflows elsewhere, making the flow of the working gas through theregenerator 8 uneven. This makes it impossible to use the wholeregenerator 8 effectively for heat storage, and thus lowers regeneratedheat exchange efficiency, degrading the performance of the Stirlingrefrigerating machine.

[0009] The working gas sealed in the cylinder 1 sometimes containsmoisture, and the moisture may freeze inside the expansion space 7 andstick to the displacer 2, causing friction between the displacer 2 andthe cylinder 1 and thereby hindering smooth sliding. This, too, degradesthe performance of the Stirling refrigerating machine.

[0010] The moisture may also condense inside the expansion space 7 andflow into the gaps between different layers of the film, hindering theflow of the working gas through those gaps and thereby making itimpossible to use the whole regenerator 8 effectively for heat storage.This, too, degrades the performance of the Stirling refrigeratingmachine.

DISCLOSURE OF INVENTION

[0011] An object of the present invention is to provide a Stirlingrefrigerating machine in which the unevenness of the flow of the workinggas passing through the regenerator has been alleviated to achievehigher regenerated heat exchange efficiency. Another object of thepresent invention is, in a Stirling refrigerating machine, to removemoisture contained in the working gas and thereby prevent degradation ofthe performance of the Stirling refrigerating machine resulting fromcondensation or freezing of the moisture. Still another object of thepresent invention is, in a Stirling refrigerating machine, to removeimpurities contained in the working gas and thereby prevent clogging ofthe regenerator caused by the impurities.

[0012] To achieve the above objects, according to the present invention,a Stirling refrigerating machine is provided with: a piston and adisplacer provided coaxially inside a single cylinder and reciprocatingaxially inside the cylinder with identical periods but with differentphases; an expansion space formed by partitioning off one end portion ofthe inside of the cylinder with the displacer; a compression spaceformed by partitioning off a middle portion of the inside of thecylinder with the displacer and the piston; and a regenerator providedin the flow path for a working medium formed between the outside of themovement path of the displacer and the inner surface of the cylinder.Here, uniformizing means for making the flow of the working mediumpassing through the regenerator uniform is provided on one or both ofthe expansion-space and compression-space sides of the regenerator.

[0013] In this structure, the working medium reciprocating between theexpansion space and the compression space passes through the flowuniformizing means immediately before flowing into the regenerator. Theflow uniformizing means makes the flow of the working medium passingthrough the regenerator uniform.

[0014] Alternatively, moisture absorbing means for removing moisturecontained in the working medium is provided on one or both of theexpansion-space and compression-space sides of the regenerator.

[0015] In this structure, the working medium reciprocating between theexpansion space and the compression space passes through the moistureabsorbing means immediately before flowing into the regenerator. Themoisture absorbing means removes moisture contained in the workingmedium.

[0016] Alternatively, a filter for removing impurities contained in theworking medium is provided on one or both of the expansion-space andcompression-space sides of the regenerator.

[0017] In this structure, the working medium reciprocating between theexpansion space and the compression space passes through the filterimmediately before flowing into the regenerator. The filter removesimpurities contained in the working medium.

[0018] Alternatively, flow uniformizing means shared as moistureabsorbing means for making the flow of the working medium passingthrough the regenerator uniform and for removing moisture contained inthe working medium is provided on one or both of the expansion-space andcompression-space sides of the regenerator.

[0019] In this structure, the working medium reciprocating between theexpansion space and the compression space passes through the flowuniformizing means shared as moisture absorbing means immediately beforeflowing into the regenerator. The flow uniformizing means shared asmoisture absorbing means makes the flow of the working medium passingthrough the regenerator uniform and removes moisture contained in theworking medium.

[0020] Alternatively, flow uniformizing means shared as a filter formaking the flow of the working medium passing through the regeneratoruniform and for removing impurities contained in the working medium isprovided on one or both of the expansion-space and compression-spacesides of the regenerator.

[0021] In this structure, the working medium reciprocating between theexpansion space and the compression space passes through the flowuniformizing means shared as a filter immediately before flowing intothe regenerator. The flow uniformizing means shared as a filter makesthe flow of the working medium passing through the regenerator uniformand removes impurities contained in the working medium

[0022] Alternatively, moisture absorbing means shared as a filter forremoving moisture and impurities contained in the working medium isprovided on one or both of the expansion-space and compression-spacesides of the regenerator.

[0023] In this structure, the working medium reciprocating between theexpansion space and the compression space passes through the moistureabsorbing means shared as a filter immediately before flowing into theregenerator. The moisture absorbing means shared as a filter removesmoisture and impurities contained in the working medium.

[0024] Alternatively, flow uniformizing means shared as moistureabsorbing means and as a filter for making the flow of the workingmedium passing through the regenerator uniform and for removing moistureand impurities contained in the working medium is provided on one orboth of expansion-space and compression-space sides of the regenerator.

[0025] In this structure, the working medium reciprocating between theexpansion space and the compression space passes through the flowuniformizing means shared as moisture absorbing means and as a filterimmediately before flowing into the regenerator. The flow uniformizingmeans shared as moisture absorbing means and as a filter makes the flowof the working medium passing through the regenerator uniform andremoves moisture and impurities contained in the working medium.

[0026] The flow uniformizing means, moisture absorbing means, filter,flow uniformizing means shared as moisture absorbing means, flowuniformizing means shared as a filter, moisture absorbing means sharedas a filter, or flow uniformizing means shared as moisture absorbingmeans and as a filter may be made of a material having an adequate heatcapacity, so that they are given the ability to store a certain amountof heat.

BRIEF DESCRIPTION OF DRAWINGS

[0027]FIG. 1 is a sectional view schematically showing a Stirlingrefrigerating machine according to the invention.

[0028]FIG. 2 is a perspective view of the flow uniformizer used in theStirling refrigerating machine according to the invention.

[0029]FIG. 3 is a sectional view schematically showing an example of aconventional Stirling refrigerating machine.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] Hereinafter, an embodiment of the present invention will bedescribed with reference to the drawings. FIG. 1 is a sectional viewschematically showing a Stirling refrigerating machine according to theinvention, and FIG. 2 is a perspective view of the flow uniformizer usedin the Stirling refrigerating machine according to the invention. It isto be noted that, in FIG. 1, such members as are found also in theconventional Stirling refrigerating machine shown in FIG. 3 areidentified with the same reference numerals, and their detailedexplanations will be omitted.

[0031] The structure shown in FIG. 1 differs from that of theconventional Stirling refrigerating machine shown in FIG. 3 only in thatflow uniformizers 11 are additionally provided contiguous with theregenerator 8, one on the expansion space 7 side thereof and another onthe compression space 6 side thereof. As shown in FIG. 2, the flowuniformizer 11 according to the invention is a doughnut-shaped memberhaving a thickness of about 1 mm to 5 mm. The flow uniformizer 11 is afilter made of, for example, polyurethane foam, and the fineness of itsmesh is so set as to produce the desired pressure loss between thecompression space 6 and the expansion space 7 when the flow path for theworking gas is formed by coupling the regenerator 8,high-temperature-side heat exchanger 9, low-temperature-side heatexchanger 10, and flow uniformizer 11 together.

[0032] When the Stirling refrigerating machine structured in this way isoperated, as indicated by the arrow A or B in the figure, the workinggas moves from one of the compression space 6 and the expansion space 7to the other. Meanwhile, the flow uniformizer 11, which providesresistance to the working gas passing through it, makes the working gasdisperse all around the flow uniformizer 11 while passing through it.Thus, after passing through the flow uniformizer 11, the working gas hassubstantially uniform flow speed at the entrance of the regenerator 8.Thus, the flow uniformizer 11, by making the working gas flow uniformlyall around the regenerator 8, achieves an adequate flow uniformizingeffect.

[0033] Table 1 shows the coefficient of performance (COP) of theStirling refrigerating machine as observed when the flow uniformizers 11are provided and when they are not (i.e. as in the conventional exampleshown in FIG. 3). Here, the temperature conditions are assumed to be 30°C. at the high-temperature side (compression space 6 side) and −23° C.at the low-temperature side (expansion space 7 side). TABLE 1 COP (−23°C. at low-temperature side, Flow Uniformizers 30° C. at high-temperatureside) Provided 0.89 Not Provided 0.66

[0034] Table 1 clearly shows that providing the flow uniformizers 11makes the flow of the working gas passing through the regenerator 8uniform, and thereby permits the whole regenerator 11 to be usedeffectively for heat storage, with the result that the Stirlingrefrigerating machine offers enhanced performance.

[0035] Needless to say, the flow uniformizers 11 may be made of anyother material than polyurethane foam to achieve the same effects, aslong as they have adequate mesh not to produce an extremely highpressure loss.

[0036] Incidentally, by making the flow uniformizers 11 of a highlymoisture-absorbing, water-absorbing material, it is possible, inaddition to making the flow of the working gas uniform, to removemoisture contained in the working gas.

[0037] Examples of such materials include: fiber of cotton, wool, silk,rayon, acetate, cellulose, hydrophilic or hydrophobic polyester, ormoisture-absorbing or water-absorbing nylon; super absorbent highpolymer materials such as fiber based on cross-linked polyacrylates; andporous materials such as zeolite, silica, diatomaceous earth, allophane,alumina-silica, zirconium phosphate, and porous metal materials.

[0038] Of these materials, a material in fiber form is formed into aflat sheet, honeycomb, corrugate sheet, or the like; on the other hand,a material in non-fiber form is sintered into a doughnut shape, or itspowder is sandwiched between pieces of nonwoven cloth together with abinder and fixed. In one of these ways, the moisture-absorbing flowuniformizer 11 shaped as shown in FIG. 2 can be easily produced.

[0039] The flow uniformizers 11 thus produced are dried to an adequatedegree, and are then arranged inside the Stirling refrigerating machineas shown in FIG. 1. This makes it possible to absorb moisture containedin the working gas and, even if the moisture condenses, to absorb thewater quickly. Thus, it is possible to prevent the moisture fromfreezing at the expansion space 7 side and sticking to the displacer 2or the like, and thereby prevent degradation of the refrigeratingperformance of the Stirling refrigerating machine, or it is possible toprevent the moisture from condensing in the expansion space 7 andstopping the gaps between different layers of the film of theregenerator 8, and thereby prevent degradation of the refrigeratingperformance. Instead of giving a single flow uniformizer 11 both theability to make working gas flow uniform and the ability to absorbmoisture, it is also possible to build a flow uniformizer and amoisture-absorber each separately.

[0040] Moreover, by making the flow uniformizers 11 of zeolite, filterpaper, or the like, it is possible, in addition to making the flow ofthe working gas uniform and absorbing moisture and water as describedabove, to absorb and remove impurities such as particles shaved off thecomponents through which the working gas reciprocates or particles of acoating agent or the like flaked off the surface of those components.This makes it possible to prevent the impurities from causing theregenerator 8 to clog and degrading the performance of the Stirlingrefrigerating machine. Instead of giving a single flow uniformizer 1 1the ability to make working gas flow uniform, the ability to absorbmoisture, and the ability to filter out impurities all together, it isalso possible to combine together two among a flow uniformizer, amoisture-absorber, and a filter, or to build them each separately.

[0041] Furthermore, by making the flow uniformizer 11 of a materialhaving an adequate heat capacity (for example, a material based onpolyester), it is possible to store heat not only in the regenerator 8but, for a certain amount of heat, also in the flow uniformizer 11. Thishelps enhance regenerated heat exchange efficiency.

[0042] Although the embodiment described above deals with a case whereflow uniformizers 11 are provided on both the expansion-space 7 andcompression-space 6 sides of the regenerator 8, they do not necessarilyhave to be provided on both sides; that is, it is also possible toprovide one flow uniformizer on one side. This helps reduce the numberof components needed and thereby reduce costs.

[0043] Obviously, many modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced other than as specifically described.

Industrial Applicability

[0044] As described above, according to the present invention, flowuniformizing means for making the flow of a working medium uniform isprovided contiguous with a regenerator forming a flow path of theworking medium reciprocating between an expansion space and acompression space formed inside a cylinder of a Stirling refrigeratingmachine. This alleviates the unevenness of the flow of the workingmedium passing through the regenerator, leading to enhanced regeneratedheat exchange efficiency and thus to enhanced performance of theStirling refrigerating machine.

[0045] Moreover, according to the present invention, the flowuniformizing means is shared as moisture-absorbing means for removingmoisture contained in the working medium. This makes it possible toprevent degradation of refrigerating performance resulting from themoisture freezing at the expansion space side, or to prevent degradationof refrigerating performance resulting from the moisture condensing inthe expansion space and stopping the gaps between different layers ofthe film of the regenerator.

1. (Amended) A Stirling refrigerating machine comprising: a piston and adisplacer provided coaxially inside a single cylinder and reciprocatingaxially inside the cylinder with identical periods but with differentphases; an expansion space formed by partitioning off one end portion ofan inside of the cylinder with the displacer; a compression space formedby partitioning off a middle portion of the inside of the cylinder withthe displacer and the piston; and a regenerator provided in a flow pathfor a working medium formed between an outside of a movement path of thedisplacer and an inner surface of the cylinder, wherein flowuniformizing means for making flow of the working medium passing throughthe regenerator uniform is provided on one or both of expansion-spaceand compression-space sides of the regenerator.
 2. A Stirlingrefrigerating machine as claimed in claim 1, wherein the flowuniformizing means is made of a material having an adequate heatcapacity.
 3. (Amended) A Stirling refrigerating machine comprising: apiston and a displacer provided coaxially inside a single cylinder andreciprocating axially inside the cylinder with identical periods butwith different phases; an expansion space formed by partitioning off oneend portion of an inside of the cylinder with the displacer; acompression space formed by partitioning off a middle portion of theinside of the cylinder with the displacer and the piston; and aregenerator provided in a flow path for a working medium formed betweenan outside of a movement path of the displacer and an inner surface ofthe cylinder, wherein moisture absorbing means for removing moisturecontained in the working medium is provided on one or both ofexpansion-space and compression-space sides of the regenerator.
 4. AStirling refrigerating machine as claimed in claim 3, wherein the flowuniformizing means is made of a material having an adequate heatcapacity.
 5. (Amended) A Stirling refrigerating machine comprising: apiston and a displacer provided coaxially inside a single cylinder andreciprocating axially inside the cylinder with identical periods butwith different phases; an expansion space formed by partitioning off oneend portion of an inside of the cylinder with the displacer; acompression space formed by partitioning off a middle portion of theinside of the cylinder with the displacer and the piston; and aregenerator provided in a flow path for a working medium formed betweenan outside of a movement path of the displacer and an inner surface ofthe cylinder, wherein a filter for removing impurities contained in theworking medium is provided on one or both of expansion-space andcompression-space sides of the regenerator.
 6. A Stirling refrigeratingmachine as claimed in claim 5, wherein the flow uniformizing means ismade of a material having an adequate heat capacity.
 7. (Amended) AStirling refrigerating machine comprising: a piston and a displacerprovided coaxially inside a single cylinder and reciprocating axiallyinside the cylinder with identical periods but with different phases; anexpansion space formed by partitioning off one end portion of an insideof the cylinder with the displacer; a compression space formed bypartitioning off a middle portion of the inside of the cylinder with thedisplacer and the piston; and a regenerator provided in a flow path fora working medium formed between an outside of a movement path of thedisplacer and an inner surface of the cylinder, wherein flowuniformizing means shared as moisture absorbing means for making flow ofthe working medium passing through the regenerator uniform and forremoving moisture contained in the working medium is provided on one orboth of expansion-space and compression-space sides of the regenerator.8. A Stirling refrigerating machine as claimed in claim 7, wherein theflow uniformizing means shared as moisture absorbing means is made of amaterial having an adequate heat capacity.
 9. (Amended) A Stirlingrefrigerating machine comprising: a piston and a displacer providedcoaxially inside a single cylinder and reciprocating axially inside thecylinder with identical periods but with different phases; an expansionspace formed by partitioning off one end portion of an inside of thecylinder with the displacer; a compression space formed by partitioningoff a middle portion of the inside of the cylinder with the displacerand the piston; and a regenerator provided in a flow path for a workingmedium formed between an outside of a movement path of the displacer andan inner surface of the cylinder, wherein flow uniformizing means sharedas a filter for making flow of the working medium passing through theregenerator uniform and for removing impurities contained in the workingmedium is provided on one or both of expansion-space andcompression-space sides of the regenerator.
 10. A Stirling refrigeratingmachine as claimed in claim 9, wherein the flow uniformizing meansshared as a filter is made of a material having an adequate heatcapacity.
 11. (Amended) A Stirling refrigerating machine comprising: apiston and a displacer provided coaxially inside a single cylinder andreciprocating axially inside the cylinder with identical periods butwith different phases; an expansion space formed by partitioning off oneend portion of an inside of the cylinder with the displacer; acompression space formed by partitioning off a middle portion of theinside of the cylinder with the displacer and the piston; and aregenerator provided in a flow path for a working medium formed betweenan outside of a movement path of the displacer and an inner surface ofthe cylinder, wherein moisture absorbing means shared as a filter forremoving moisture and impurities contained in the working medium isprovided on one or both of expansion-space and compression-space sidesof the regenerator.
 12. A Stirling refrigerating machine as claimed inclaim 11, wherein the moisture absorbing means shared as a filter ismade of a material having an adequate heat capacity.
 13. (Amended) AStirling refrigerating machine comprising: a piston and a displacerprovided coaxially inside a single cylinder and reciprocating axiallyinside the cylinder with identical periods but with different phases; anexpansion space formed by partitioning off one end portion of an insideof the cylinder with the displacer; a compression space formed bypartitioning off a middle portion of the inside of the cylinder with thedisplacer and the piston; and a regenerator provided in a flow path fora working medium formed between an outside of a movement path of thedisplacer and an inner surface of the cylinder, wherein flowuniformizing means shared as moisture absorbing means and as a filterfor making flow of the working medium passing through the regeneratoruniform and for removing moisture and impurities contained in theworking medium is provided on one or both of expansion-space andcompression-space sides of the regenerator.
 14. A Stirling refrigeratingmachine as claimed in claim 13, wherein the flow uniformizing meansshared as moisture absorbing means and as a filter is made of a materialhaving an adequate heat capacity.